Transformer



M, DAM w, n m D" A M m A G .m ...................A F W...A.......................

Jan. 14, 1947. G. A. Ewls Y 2,414,232

TRANSFORMER Filed Jan.- 2, 1945 4 Sheets-Sheet .'5

y @zo VfR/2 fw/5' 5 i INVENTOR.

Jan. 14, 1947. G, A, LEWS 2,414,232

TRANSFORMER .Filed Jan. 2, 1945 4 Sheets-Sheet 4 FT-5.11. g/ y Patente-d Jan. 14, 1947 y UNITED STATES PATENT OFFICE 'rRANsFoRMER Glover A. Lewis, Houston, Tex. Application January 2, 1945, serial No. 571,053

` claims. (cl. 17a-119) This application is-in part a continuation of my prior copending application Serial No. 408,008, led August 23, 1941.-

This invention relates to transformers and has for its general object the provision of a transformer in .which the output current and voltage can be morej'accurately controlled than in previous types of transformers.

In various types of work, and particularly the electrical welding service, it is essential that a transformer for producing the current to be used be capable of very accurate control in so far as its current and voltage characteristics are concerned. Various attempts have been made in the past to provide transformers having the desired characteristics, but in every instance certain undesirable characteristics have accompanied the desirable characteristics obtained. For example, it has not been possible with previous constructions to provide for a substantially constant current output from the secondary coil of the transformer without the characteristics of the output current with respect to its wave form, etc. changing greatly as the load changes. It has also been impossible with previous known transformer constructions to alter the open circuit voltage of the secondary coil.

It is an object of this invention, therefore, to provide a transformer in which the voltage of the secondary coil may be controlled to vary as desired as the current in the secondary coil varies.

It is a further and more specific object of this invention to provide a transformer in which the voltage supplied by the secondary coil will drop as the current flowing in the secondary coil increases in value so that by an increase in the current flowing in the secondary coil, the voltage across the secondary coil may be made to vary from a maximum to substantiallyzero.

It is a further object of this invention to provide a transformer of the type referred to in which the open circuit voltage of the secondary coil may be adjusted to whatever value ma.v be desired.

It is a further object of this invention to provide a transformer ofthe type referred to in which the secondary coil will provide a substantially constant current output over a wide range of resistance in the secondary coil circuit.

Another and more specific object is to provide a transformer which will supply a substantially constant current to an arc of varying length.

Another object of this invention is to provide a transformer in which a predetermined reactance will be present in the secondary circuit and to provide means whereby said reactance may be adjusted.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is illustrated one embodiment of this invention.

In the drawings:

Fig. 1 shows a side elevation of a welding machine including a transformer constructed in accordance with this invention.

Fig. 2 is a horizontal transverse section substantially on the line 3-3 of Fig. 3.

' Fig. 3 is a side elevation of the same machine with the guard removed, showing the relative positions of the various parts of the transformer.

Fig. 4 is a view similar to Fig. 2, but with the guard removed.

Fgf is a side elevation showing the coil arrangement of the transformer, the other parts thereof being removed for the purpose of simplifying the illustration.

Fig.` 6 shows an elevation of the same structure as illustrated in Fig. 5 taken at right angles thereto.

Fig. 7 is a top plan view of the structure shown in Fig. 5.

Fig. 8 shows the electrical diagram and illustrates the connectionsbetween the various coils shown in Figs. 5 to 7 inclusive. Fig. 9 is a top plan view of the secondary coil forming a part of this invention, parts of the covering for the same having been broken away and shown in cross section for the purpose of illustration.

Fig. 10 is a fragmentarywgiew illustrating the manner of arranging the windings of the secondary coil shown in Fig. 9.

Fig. 11 shows a longitudinal cross section of the composite winding illustrated in Fig. 10.

' Although a transformer constructed in accordance with this invention may be mounted in any desired manner most convenient for the use to which it is to be put, one desired form is illustrated in Figs. l to 4 inclusive. In these figures it will be seen that the, transformer is built on a frame presently to be described, and that this frame adjacent one end carries an axle I, on the opposite ends of which are mounted wheels 2. Adjacent the opposite end the frame is provided with a swivel mounting 3 on which is carried acaster wheel Thus, a three-wheel support is provided for the device so that it may be readily transported to any location desired.

For further ease in transporting the machine,

asi-gasa .it is provided with a pair of upwardly and rearwardly inclined bars adjacent one end, these bars being joined at their upper and rear-most ends by means of a cross bar t. The bars 5 are secured by a suitable means, such as welding or the like, to the frame of the transformer at their lower ends l and at some intermediate point. such as the point 3.

The transformer may be handled and transported from one place to another by means of a crane or a hoist and for this purpose there is provided a Abail 9 adapted to be engaged by a hook or other connecting member carried by such hoist.

For the purpose of protecting workmen against accidental contact with parts of the transformer, which might be charged with high vo1tage,-and

for the purpose of protecting the transformer against accidental damage caused by heavy or sharp objects being brought into contact therewith, the entire body of the transformer is preferably enclosed by panels 9 of sheet metal, or any other desirable material, and part of this enclosure preferably is in the form of a wire mesh I0, so as to provide ample circulation of air for the purpose of cooling the transformer. Also, a door II may be provided for the purpose of permitting access to the terminal board of the secondary coil, as will be presently described. On the outside of the housing, and preferably adjacent the han` die bars 5, will be located the main switch I2, controlling the supply to the primary of the transformer.

Referring now more particularly to Figs. 3 and 4, it will be seen that the frame members I3 and i4, which are directly supportedby the wheels 2 members I3 to the other member I3. There are two such vangle irons I5 which are clamped to the opposite sides of the core I6 of the transformer by means of bolts I'I, or the like.

The core I6 is shown as comprising a rectangular frame, having end portions, side portions 20, and a center leg 2l, thus forming two windows I8 and I9 therethrough. The frame and windows are vertically disposed. 'I'he aggregate cross-sectional area of the side portions 2l! of the core is the same as the cross-sectional area of the center leg 21, as best shown in Fig. 2. 'I'he same is true of the aggregate cross-sectional*` area of the end portions. Thus the side and end portions of the core have a joint flux-carrying capacity equal to that of the center leg. Hence the core provides a closed magnetic circuit of substantially i I5. At their upper ends these straps are bolted to the downwardly extended flanges of the angle irons 24., the upper flanges of which extend toward each other across the top of the core. irons 24 extend along the entire length of the upper cross member of the core and serve as a support for the gear box 25, the same being secured thereto by cap-screws 26.

Surrounding the center leg 2l of the core and extending through the windows I8 and I9 thereof, adjacent their upper ends, is the primary coil 28. This primary coil may be of any. desired form and the leads 29 therefrom extend to the switch I2, through'which this coil is supplied with suit- The angle I able current. The primary coil is supported by means of a pair of insulating beams 3G, which are in turn carried on the brackets 3i and these brackets are welded or otherwise suitably secured to the straps 2 I as shown at 32.

The secondary coil 33 ofthe transformer likewise surrounds the center leg 2l of the core and is carried on insulating beams 3G, which are in turn supported by bars 35 extending through the interior of the secondary coil. These bars are secured at their upper ends to the lower ends oiav pair of cables 36, which are in turn carried by the sheaves 31 on the gear box 25. The sheaves 3l are adapted to be rotated to raise or lower the secondary coil 33 by means of a crank 38 that serves to actuate the gears within the gear box` 25 for this purpose. By the means just described, the secondary coil may be located at any level desired between its lowermost position, inwhich it rests upon the angle supports I5, and its upper position, in which it would contact the beams 30.

The terminals 39 and til of the secondary coil are connected through flexible conductors di and l2 with suitable binding posts 53 and @it on the terminal board 45, which is provided for this purpose. The terminal board is mountedin a stationary positionv by means of suitable brackets 46, welded or otherwise suitably secured to the straps 20, or to any other suitable stationary portion of the frame of the transformer.

'I'he secondary coil 33 is of a special construction illustrated in Figs. 9 to 1l inclusive, as will be presently described.

Disposed inside the windows I8 and I9 and extending through these windows, but in a substantially vertical position, are auxiliary coils 47 and 38. These coils are adapted to control the leakage flux between the primary and secondary coils of the transformer when under load, as hereiniafter explained, so as to control the output voltage of the transformer under load. Leakage flux as here used, is that ux which links the primary or the secondary coil but not both, and which is due toand exists only during the loading of the secondary. These auxiliary coils are preferably wound at in the form ordinarily called "pan-cake coils and are not provided with a magnetic core. Instead they are merely coils withv an air core. These two auxiliary coils have their similar ends connected by means of the conductor Q9, which may be integral with the conductors forming the two coils. The other like ends of these coils are connected by conductors 50 and 5I respectively with suitable binding posts.

43 and 52 on the terminal board 45. It will be noted thatthe binding pbst 43 serves as the terminal both for one end of the'secondary coil 33 and for one end of the auxiliary coil 48. The load may then be taken from the binding posts 4B and 52, which will place the secondary coil 33 in series with the two auxiliary coils. 1f it be desired to use the transformer without the two auxiliary coils, the load may be taken from the binding posts 33 and 34. Access to the terminal board 45 may be had as heretofore stated through the door Il in the housing. It should be noted also that the frame outside the housing is provided with a pair of upstanding posts 53 of any suitable form upon which the leads for connecting the secondary coil to the work may be wound when not in use.

The secondary coil is preferably formed as ininsulatedfromeachotherbynysuitable insulating covering. such as the tape il, 'or any enamel or any other form of insulation that may be found desirable. The -turns themselves are each made up of ltwo parallel ribbons 56 of copper or otherextend a substantial distance axially of the coil and parallel with the leg 21 of the core. These iron sheets preferably extend only along those portions of the coil which areto be disposed within or closely adjacent tothe core windows. It has been found that if these soft iron laminations are permitted to extend substantially outside of the core windows they will cause obiec tionable heating of the coil. However, such extension of the magnetic laminations 51 would not prevent the operation of the device in the manner hereinafter described. Y y

In operation the parts will be assembled as indicated in Figs. 1 to 4 inclusive. A source of alternating current, electrical energy of the proper frequency and voltage, for which the machine may be designed, is connected to the primary coil through the controllingswitch i2. The leads which are adapted to conduct electricity from the secondary coil to the point where it is to be used may be secured either to the binding posts 44 and 52, or to the binding posts I3 and 44, accord ing to the operation desired.

At this point the open circuit voltage of the secondary may be adjusted by raising or lowering the secondary coil through the use of the crank 38, the fgears within the gear box 2i, the sheaves 31 andthe wheels 36, which suspend the secondaryl coil, It is noteworthy that ordinarily the moving of, the secondary coil, located as this secondary coil is located, toward or away from the primary coil'would not change its open circuit voltage. However, in the present invention, the open circuit voltage will-change as this coil is moved because of the fact that greater leakage is provided by the` presence of .the soft iron laminations 51 interposedin the windings of the secondary. The presence of the laminations provides a path for a portion of the magnetic ilux to pass between the successive convolutions of the secondary coil to the bottom cross member of the core instead ofv passing through the central window of the coil following along the leg 21 of the core as would otherwise be the case. 'Ihe amount of leakage through these soft iron laminations in the secondary winding changes as the secondary coil is` moved toward and away fromA the bottom cross member of the core, because as the coil is moved toward and awayfrom the bottom cross member of the core, these soft inserts or lamnations are brought closer to or separated further fromthe iron of the main body of the core. The result is that when this leakage is great, as when the coil is near the bottom cross member of the core. there will be less voltage generated in the secondary coil than there will be when the coil is moved farther from this bottom cross member and the leakage thus decreased.

' When a transformer of the'type to which this Interposed between the aangaan y 6 duce a stabilizing effect on the to an arc employed'in welding. By .making it possible to lreduce the open circuit voltage of the secondary coil, and by providing. a leakage path between the turnsof the secondary coil both when it is loaded and when it is open, they assist in preventing a great surge of current whe'n striking an arc, and as-the arc is maintained in the course of welding it has been found through much actual experience that the presence-of thesesoft iron sheets or laminationsftends to stabilize the i-alnount of current owi'ng from the secondary is known that the presence of thes'e .windings greatly improves the characteristics of the current iiowing from the secondary coil of a transformer, such as described, when the same is employed for arc welding purposes.

Ithas further been discovered that the presence of the soft iron laminations in the secondary causes the secondary to produce, when loaded, a

current of slightly different frequency from the possible by the laminations 51, then the take-off will be directly from the terminals of the secondary coil and the take-oli and leads will be connected to the binding posts 43 and 44,

If on the other hand, it be desired that-the leakage be controlled by the amount of current being drawn from the secondary coil, the takeoii will be from the binding posts 44 and 52, so

that the auxiliary coils 41 and 48 will be in series with the secondary coil. It will be seen that when this arrangement is employed, no current will flow in the auxiliary coils when there is no load on the secondary. Since the sideiegs 20 of th core have a total capacity for carrying magnetic flux which is equal to that of the center leg, there will be no leakage flux through the auxiliary coils when there is no current flowing in them or in the secondary except perhaps a very slight amount of flux due to self induction. Therefore, the auxiliary coils will not substantiallyailect the no load voltage supplied by the transformer. However, when the transformer secondary is loaded at all, any current flowing in the sec-Y ondary coil will also ilow through the two auxiliary coils and this current will tend to promote leakage ux through the space between the primary and secondary coils, such flux also linking either the primary or. the secondary depending.l on the direction in which the auxiliary coils are wound and connected to the secondary. In other words, if these auxiliary coils 41 and 48 are con nected with one terminal to the secondary, they would, for example, promote leakage in one direction as the flow of current increases and would hence lower the closed circuit voltage of the secdescription relates is employed in connection with arc welding, the soft iron lamination; 51 play an additional advantageous rolein that they proondary coil and limit the amount of current that can now from the secondary coil. 0n the other hand, if connected in theopposite direction, the auxiliary coils would tend to promote leakage in the opposite directionmore and more as the current owing in the secondary coil increases, and by virtue of this effect would tend to cause the current supplicav of the current produced by the secondary of the transformer may be governed so asto be more suitable for welding purposes, and whereby magnetic iiux leakage can be regulated according to the load placed on the transformer without in any way affecting the open circuit characteristics thereof.

Means has thus been provided for carrying out all the objects and advantages sought by this invention.

Having described my invention, I claim:

1. An electrical transformer having a. core with a, window therein, a secondary coil comprising a wound electrical conductor having a portion thereof passing through said window and.means providing a'path for magnetic ux between the windings of said conductor, said last mentioned means comprising a body of magnetic material interposed between each of a plurality of adjacent portions of said conductor of said Secondary coil and being continuous along those portions of the secondary coil which pass through the window of the transformer core, said body being in electrical contact substantially throughout its extent with an adjacent winding ofv said secondary coil.

2. An electrical transformer having a core with a window therein, a secondary coil comprising a wound electrical conductor having a portion thereof passing through said window and means providing a path for magnetic ilux between the windings of said conductor, said last mentioned means comprising a body of magnetic material associated with each of a plurality of the individual turns of said secondary coil and being continuous along those portions of said secondary coil which pass through the window of the transformer core.

3. An electrical transformer having a secondary coil comprising a wound electrical conductor and means providing a path for magnetic ux between the windings of said conductor, said last mentioned means comprising a body of magnetic material incorporated in each of a plurality of adjacent turns of said secondary coil along those portions'of said secondary coil, whichare disposed. within a window of the transformer core,

and said body of magnetic material being discontinuous along those portions which do not pass through such window.

d. An electrical transformer having a secondary coil comprising a wound electrical conductor and means interposed between the windings of saidv electrical conductor providinga path for magnetic flux between said windings, said last mentioned means comprising a plurality of spaced vbodies of magnetic material interposed between adjacent windings of saidsecondary coil, said bodies being disposed along those portions of said secondary coill which are adapted to be disposed within a window of a transformer core, and those portions of the secondary coil which do not pass aaraase dow, a means for moving said secondary coil toward and away from said primary coil, said secondary coil comprising a wound electrical conductor of non-magnetic material, and bodies o! magnetic material extending along said conductor in electrical contact therewith and interposed `between the windings thereof along those portions ofA said coil which extend through said win-v dow, and said bodies of magnetic Vmaterial being discontinuous along the portions of said coil which l do not extend through said window.

6. A transformer comprisingva core having a window therein, a primary coil having a part extending through said window, a secondary coil lhaving a part extending through said window and an auxiliary coil having a core composed entirely of non-magnetic material, said rst mentioned core being so proportioned that the flux i ondary coils, and said auxiliary coil being connected in series with said secondary coil whereby a load on said secondary coil will induce av leakage ux between said primary and secondary coils.

'7. A transformer having a core providing a closed magnetic circuit of substantially uniform cross-sectional area throughout, spaced primary and secondary coils surrounding said core, and p an auxiliary coil with an air core surrounding a portion ofthe path which any leakage-flux between said primary and secondary coils would tend to take. said auxiliary coil being connected in series with said secondary coil.

closed magnetic circuit of substantially uniform cross-sectional area throughout, spaced primary 8. A transformerl having a core providing a and .secondary coils surrounding said core, and

an auxiliary coil with an air core surrounding a portion of the path which any leakage iiux between-said primary and secondary coils would tend to take, and means for passing a current' 9. A transformer having a core providing a cross-sectional area throughout, spaced primary i and secondary coils surrounding said core, andan auxiliary coil with an air core surrounding a portion of the path which any leakage flux' between l said primary and secondary coils wouldtend to take, said auxiliary coil being connected in series with said secondary coil, the connection between j said auxiliary and secondary coils being such as @o to cause an increase in the leakage through said auxiliary coil when the load on said secondary K coil is increased.'

10. A transformer having a, core includingan l ISt'-, v

' elongated portion and a cross member 'in ing said elongated portion, spaced and ,v

secondary coils surrounding saidelongated tion, saidsecondary coil being'movable,toward@`- andv away from said cross member of the core@ and means included in said secondarycoil comj` mprising a body of magnetic material interposed between the windings of the secondary "colland' j forming an increasing leakage path as said sec-1 .ondary coil is moved toward the cross member. ll. A transformer having a core including elongated portion'- and a cross member ing the same, spaced primary and secondary coils surrounding said core, said secondary coil being movable toward and away from said cross member of the core, means included in said secondary coiland forming an increasing leakage path as saidlsecondary coil is moved toward the cross member, anauxiliary coil with an air core surrounding a portion of thepath of leakage flux between said primary and secondary coils, said auxiliary coil being connected in series with said secondary coil, the connection being in such direction as to increasethe leakage through said auxiliary coil when a load is placed on said sec- `ondary coil.

12. A transformer having a core providing av closed magnetic circuit of substantially uniform cross-sectional area throughout. spaced primary and secondary coils surrounding said core, an auxiliary coil with anon-magnetic core surrounding a portion of the path which any leakage flux between said primary and secondary coils would tend to take, and means for passing a cur' vrent through said auxiliary coil.

13. A power distribution transformer having a core providing a closed magnetic circuit of substantially uniform cross-sectional area throughout, spaced primary and secondary coils surrounding said core, and an' auxiliary coil with a non-magnetic -core surrounding a portion of the path which any leakagefiux between said pria portion thereof passing through said window, said coil being formed of a wound composite con- A ductor comprising a pair of conducting strips, and

a body of magnetic material interposed between said conducting strips along those portions of the v coil which pass through the window oi the transformer core, said body providing a path for magnetic flux.

15. An electrical transformer having a core constituting a closed magnetic circuit and comprising a frame having cross-members connected by a central leg, primary and secondary coils surrounding said central leg, said secondary coil comprising a conducting ribbon, and sheets -of v magnetic material interposed between turns of said ribbon, said sheets extending a substantial distance axially of said coil parallel with said leg and providing leakage paths through said coil over which magnetic ux may pass to or from one oi said cross-members. y

GLDVER A. LEWIS. 

